Re: [PATCH 2/4] perf hist: Simplify hist printing logic for group events

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Feb 14, 2024 at 3:57 PM Ian Rogers <irogers@google.com> wrote:
>
> On Mon, Feb 12, 2024 at 11:53 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > It can uses an array to save the period (or percent) values for member
> > events and print them together in a loop.  This simplify the logic to
> > handle missing samples in members with zero values.
> >
> > No functional change intended.
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/perf/ui/hist.c | 55 +++++++++++++++++---------------------------
> >  1 file changed, 21 insertions(+), 34 deletions(-)
> >
> > diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
> > index 2bf959d08354..5f4c110d840f 100644
> > --- a/tools/perf/ui/hist.c
> > +++ b/tools/perf/ui/hist.c
> > @@ -33,6 +33,7 @@ static int __hpp__fmt(struct perf_hpp *hpp, struct hist_entry *he,
> >         char *buf = hpp->buf;
> >         size_t size = hpp->size;
> >
> > +       /* print stand-alone or group leader events separately */
> >         if (fmt_percent) {
> >                 double percent = 0.0;
> >                 u64 total = hists__total_period(hists);
> > @@ -45,12 +46,19 @@ static int __hpp__fmt(struct perf_hpp *hpp, struct hist_entry *he,
> >                 ret = hpp__call_print_fn(hpp, print_fn, fmt, len, get_field(he));
> >
> >         if (evsel__is_group_event(evsel)) {
> > -               int prev_idx, idx_delta;
> > +               int idx;
> >                 struct hist_entry *pair;
> >                 int nr_members = evsel->core.nr_members;
> > +               union {
> > +                       u64 period;
> > +                       double percent;
> > +               } *val;
> >
> > -               prev_idx = evsel__group_idx(evsel);
> > +               val = calloc(nr_members, sizeof(*val));
> > +               if (val == NULL)
> > +                       return 0;
>
> Looks good, but should this return value be negative to indicate an
> error? Snprintf gives a negative result on error, its result is
> sometimes returned from hpp__fmt_acc, as is this result.

Sounds good, will change.

Thanks,
Namhyung

>
> >
> > +               /* collect values in the group members */
> >                 list_for_each_entry(pair, &he->pairs.head, pairs.node) {
> >                         u64 period = get_field(pair);
> >                         u64 total = hists__total_period(pair->hists);
> > @@ -59,47 +67,26 @@ static int __hpp__fmt(struct perf_hpp *hpp, struct hist_entry *he,
> >                                 continue;
> >
> >                         evsel = hists_to_evsel(pair->hists);
> > -                       idx_delta = evsel__group_idx(evsel) - prev_idx - 1;
> > -
> > -                       while (idx_delta--) {
> > -                               /*
> > -                                * zero-fill group members in the middle which
> > -                                * have no sample
> > -                                */
> > -                               if (fmt_percent) {
> > -                                       ret += hpp__call_print_fn(hpp, print_fn,
> > -                                                                 fmt, len, 0.0);
> > -                               } else {
> > -                                       ret += hpp__call_print_fn(hpp, print_fn,
> > -                                                                 fmt, len, 0ULL);
> > -                               }
> > -                       }
> > -
> > -                       if (fmt_percent) {
> > -                               ret += hpp__call_print_fn(hpp, print_fn, fmt, len,
> > -                                                         100.0 * period / total);
> > -                       } else {
> > -                               ret += hpp__call_print_fn(hpp, print_fn, fmt,
> > -                                                         len, period);
> > -                       }
> > +                       idx = evsel__group_idx(evsel);
> >
> > -                       prev_idx = evsel__group_idx(evsel);
> > +                       if (fmt_percent)
> > +                               val[idx].percent = 100.0 * period / total;
> > +                       else
> > +                               val[idx].period = period;
> >                 }
> >
> > -               idx_delta = nr_members - prev_idx - 1;
> > -
> > -               while (idx_delta--) {
> > -                       /*
> > -                        * zero-fill group members at last which have no sample
> > -                        */
> > +               /* idx starts from 1 to skip the leader event */
> > +               for (idx = 1; idx < nr_members; idx++) {
> >                         if (fmt_percent) {
> >                                 ret += hpp__call_print_fn(hpp, print_fn,
> > -                                                         fmt, len, 0.0);
> > +                                                         fmt, len, val[idx].percent);
> >                         } else {
> >                                 ret += hpp__call_print_fn(hpp, print_fn,
> > -                                                         fmt, len, 0ULL);
> > +                                                         fmt, len, val[idx].period);
> >                         }
> >                 }
> > +
> > +               free(val);
> >         }
> >
> >         /*
> > --
> > 2.43.0.687.g38aa6559b0-goog
> >